Need help with fuel problem.

[JDW 88]

I have purchased what appeared to be mainly stock 88 5.0 5 speed coupe last October. The car is still speed density and has the following mods on it

Underdrives
K & N in box filter
Mac Shorties, Power Box and Pro Dumps
Taylor Custom fit 8mm wires

Parts replaced:
Map Sensor
Plugs
Oxygen Sensors

My problem #1,

I am flooding out at idle and backfiring badly. I have 55 lbs of fuel pressure at the rail at idle and a factory fuel regulator. Will it help to replace the regulator with an adjustable one to drop the pressure down. Where else should I look to fix this problem.

Problem # 2,
No check engine light a mechanic friend of mine said some cars will not run without the light being active any ideals on how to fix it?